package com.huitone.gddw.utils;

import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics2D;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.util.Date;
import java.util.Random;

import javax.imageio.ImageIO;
import javax.servlet.ServletException;
import javax.servlet.ServletOutputStream;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;

/**
 * 关于验证码的工具类
 * @author wuluodan
 *
 */
public final class CaptchaUtil {

	private CaptchaUtil() {}
    
    /**
     * 随机字符字典
     */
    private static final char[] CHARS = {'0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'J'
    		, 'K', 'L' , 'M', 'N', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z'};
    
    /**
     * 随机数
     */
    private static Random random = new Random();
    
    /**
     * 获取4位随机数
     */
    private static String getRandomString() {
        StringBuffer buffer = new StringBuffer();
        for (int i = 0; i < 4; i++) {
            buffer.append(CHARS[random.nextInt(CHARS.length)]);
        }
        return buffer.toString();
    }
    
    /**
     * 获取随机数颜色
     */
    private static Color getRandomColor() {
        return new Color(random.nextInt(255),random.nextInt(255), random.nextInt(255));
    }
    
    /**
     * 返回某颜色的反色
     */
    private static Color getReverseColor(Color c) {
        return new Color(255 - c.getRed(), 255 - c.getGreen(), 255 - c.getBlue());
    }
    
    public static void outputCaptcha(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // 禁止图像缓存
        response.setHeader("Pragma", "no-cache");
        response.setHeader("Cache-Control", "no-cache");
        response.setDateHeader("Expires", 0);
        response.setContentType("image/jpeg");

        // 计算验证码有效期毫秒数
        Long captchaValidTime = Long.parseLong(ContextPropertiesUtils.getProperty("captcha_valid_time")) * 1000;
        
        // 将四位数字的验证码保存到 session 中
        String randomString = getRandomString();
        HttpSession session = request.getSession(true);
        session.setAttribute("captcha", randomString);
        session.setAttribute("captchaDate", new Date(new Date().getTime() + captchaValidTime));

        int width = 100;
        int height = 30;

        Color color = getRandomColor();
        Color reverse = getReverseColor(color);

        BufferedImage bi = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);
        Graphics2D g = bi.createGraphics();
        g.setFont(new Font(Font.SANS_SERIF, Font.BOLD, 16));
        g.setColor(color);
        g.fillRect(0, 0, width, height);
        g.setColor(reverse);
        g.drawString(randomString, 18, 20);
        for (int i = 0, n = random.nextInt(100); i < n; i++) {
            g.drawRect(random.nextInt(width), random.nextInt(height), 1, 1);
        }

        // 转成 JPEG 格式
        ServletOutputStream out = response.getOutputStream();
        ImageIO.write(bi, "jpeg", out);
//        JPEGImageEncoder encoder = JPEGCodec.createJPEGEncoder(out);
//        encoder.encode(bi);
        out.flush();
    }
	
}
